1. Field of the Invention
The present invention relates generally to cancer detection and therapy. The invention is more particularly related to polynucleotides encoding polypeptides involved in the metabolism of sphingolipids, polypeptides, and to agents that modulate the expression and/or activity of such polypeptides. Such agents may be used, for example, to diagnose and/or treat cancers such as breast, colon, uterus, stomach, ovary, lung, kidney and rectum cancer, the diagnosis and treatment of muscle developmental defects and cardiomyopathy, and diagnosis and treatment of hereditary sensory neuropathy type 1 and the sphingolipidoses. The present invention further relates to methods of screening agents that modulate the expression and/or activity of polynucleotides and/or polypeptides involved in sphingolipid metabolism.
2. Description of the Related Art
Breast cancer is a significant health problem for women in the United States and throughout the world. Although advances have been made in detection and treatment of the disease, breast cancer remains the most common form of cancer, and the second leading cause of cancer death, in American women. Among African-American women and women between 15 and 54 years of age, breast cancer is the leading cause of cancer death. One out of every eight women in the United States will develop breast cancer, a risk which has increased 52% during 1950-1990. In 1994, it is estimated that 182,000 new cases of female breast cancer were diagnosed, and 46,000 women died from the disease.
No vaccine or other universally successful method for the prevention or treatment of breast cancer is currently available. Management of the disease currently relies on a combination of early diagnosis (through routine breast screening procedures) and aggressive treatment, which may include one or more of a variety of treatments such as surgery, radiotherapy, chemotherapy and hormone therapy. The course of treatment for a particular breast cancer is often selected based on a variety of prognostic parameters, including an analysis of specific tumor markers. However, the use of established markers often leads to a result that is difficult to interpret.
With current therapies, tumor invasiveness and metastasis is a critical determinant in the outcome for breast cancer patients. Although the five year survival for women diagnosed with localized breast cancer is about 90%, the five year survival drops to 18% for women whose disease has metastasized. Present therapies are inadequate for inhibiting tumor invasiveness for the large population of women with this severe disease.
Colon cancer is the second most frequently diagnosed malignancy in the United States as well as the second most common cause of cancer death. The five-year survival rate for patients with colorectal cancer detected in an early localized stage is 92%; unfortunately, only 37% of colorectal cancer is diagnosed at this stage. The survival rate drops to 64% if the cancer is allowed to spread to adjacent organs or lymph nodes, and to 7% in patients with distant metastases.
The prognosis of colon cancer is directly related to the degree of penetration of the tumor through the bowel wall and the presence or absence of nodal involvement, consequently, early detection and treatment are especially important. Currently, diagnosis is aided by the use of screening assays for fecal occult blood, sigmoidoscopy, colonoscopy and double contrast barium enemas. Treatment regimens are determined by the type and stage of the cancer, and include surgery, radiation therapy and/or chemotherapy. Recurrence following surgery (the most common form of therapy) is a major problem and is often the ultimate cause of death. In spite of considerable research into therapies for the disease, colon cancer remains difficult to diagnose and treat. In spite of considerable research into therapies for these and other cancers, colon cancer remains difficult to diagnose and treat effectively. Accordingly, improvements are needed in the treatment, diagnosis and prevention of breast and colon cancer. The present invention fulfills this need and further provides other related advantages.
Mutations that result in failure or dysregulation of sphingolipid synthesis or catabolism are directly responsible for a number of human diseases, including hereditary sensory neuropathy type 1 and the group of lysosomal storage diseases called the sphingolipidoses (Bejaoui, K., Wu, C., Scheffler, M. D., Haan, G., Ashby, P., Wu, L., de Jong, P. and Brown, R. H., Jr. (2001). Nat Genet 27, 261-2.; Dawkins, J. L., Hulme, D. J., Brahmbhatt, S. B., Auer-Grumbach, M. and Nicholson, G. A. (2001). Nat Genet 27, 309-12.; Gable, K., Han, G., Monaghan, E., Bacikova, D., Natarajan, M., Williams, R. and Dunn, T. M. (2002). J Biol Chem 277, 10194-200.). A large body of evidence now indicates that sphingolipid metabolites and enzymes of sphingolipid metabolism play important roles in regulating cell migration, stress response, survival, differentiation, senescence, apoptosis, receptor signaling, and endocytosis in eukaryotic cells. These findings suggest molecular mechanisms by which sphingolipids may affect animal physiology and contribute to disease states.
Sphingosine-1-phosphate (S-1-P) is an endogenous sphingolipid metabolite present in most mammalian cells and in serum. Like other sphingolipid metabolites such as ceramide and sphingosine, S-1-P participates in specific signal transduction pathways. Many of the effects of S-1-P signaling, which include promotion of cellular proliferation, enhancement of migration, inhibition of apoptosis and stimulation of angiogenesis, influence the transformation, growth, drug resistance, vascularity and metastatic capacity of cancer cells. Several observations support the notion that sphingosine kinase (SK) and sphingosine-1-phosphate lyase (SPL) may be cancer related genes. First, the overexpression of SK in NIH3T3 fibroblasts leads to oncogenic transformation as determined by the ability of transfected cells to form foci in vitro and to form fibrosarcomas in NOD/SCID mice. Second, human SPL was cloned and mapped to 10q21, a chromosomal region frequently deleted in a variety of human cancers. Taken together, these observations raise the possibility that SK and SPL may be potentially effective targets for pharmacological intervention in the treatment of cancer. Accordingly, the present invention provides methods for screening agents that modulate sphingolipid metabolism. Further, the present invention provides methods for detecting and treating cancer.
Critical steps in the identification and development of new therapeutic agents are: (a) generation of candidate agents; and (b) screening of the candidate agents for efficacy and safety. With the advent of combinatorial chemistry protocols, large numbers of potential compounds, known as libraries, can be rapidly generated. Such libraries serve as collections of potential therapeutic agents. Following generation of a library of potential therapeutic agents, the library must be screened to identity the promising candidates.
For screening purposes, a number of in vitro high throughput screening protocols have been developed. However, these in vitro screening assays must be followed by in vivo screening assays. Since it is undesirable to immediately screen compounds that show promise from in vitro assays in humans, an important step in the identification of therapeutic agents for such cellular proliferative diseases is the screening of potential therapeutic compounds in non-human animal models. As such, non-human animal models of cancer and other cellular proliferative diseases play an important role in the discovery of therapeutic agents for such diseases.
One type of non-human animal model that can be used for screening purposes to identify therapeutic agents for use in treating cancer and other cellular proliferative diseases is a non-human mammalian model, e.g. mice, etc. However, mice are expensive, have a slow reproduction time, and generate small numbers of offspring. As such, they are less than ideal for many high throughput screening assays.
Accordingly, there is a need for additional animal models for the identification of therapeutic agents for cancer and other diseases associated with altered sphingolipid metabolism, such as. Of particular interest would be the development of an animal model having a relatively short life span and a rapid reproduction cycle characterized by the production of large numbers of offspring. Preferably, such an animal model should also be relatively simple and economic to maintain.